Apparatus for continuously digging coal



Nov. 16, 1954 c. H. sNYDER ET Al. 2,694,562

APPARATUS FOR CONTINUOUSLY DIGGING COAL Nov. 16, 1954 c. H. sNYDl-:R ETAL APPARATUS FOR CONTINUOUSLY DIGGING COAL 6 Sheets-Sheet 5 Filed March 2. 1948 NOV- 15, 1954 c. H. sNYDER ETAL APPARATUS FOR CONTINUOUSLY DIGGING COAL Filed March 2. 1948 6 Sheets-Sheet 4 NOV. 16, 1954 Q H SNYDERv ETAL I APPARATUS FOR CONTINUOUSLY DIGGING COAL Filed March 2, 1948 6 Shee'ts-Sheet 5 W15/n Arran/vf Y.

c/H. sNYDER ETAL APPARATUS FOR` CONTINUOUSLY DIGGING COAL Nov. 16, 1954 e sheets-sheet e Filed March 2. 1948 United States Patent O APPARATUS FR CONTINUOUSLY DIGGING COAL Clifford H. Snyder, Dormont, Arnold E. Lamm, Mount Lebanon, and William D; Carothers, Crafton, Pa.,l and Vincent J. McCarthy, Youngstown, Ohio, assignors, by mesne assignments, to. The Colmol Company, New Lexington, Ohio, a corporation of Ohio- Application March 2, 1948, Serial No. 12,626

52 Claims. (Cl. 262-9) This invention relates generally to mining, and.y more particularly to new and improved apparatus for the min` ing of coal and in its more specific aspect contemplates the continuous mining of coal.

The present general practice of deep coal mining necessitates a series of steps performed in cycles by the aid of different machines. The first step is effected by cutting bars provided with endless chainsv containing bits that undercut the coal, which is in reality a milling process producing great quantities of bug-dust or fines that is a source of many mine explosions. The undercutting may be supplemented by side cutting or sometimes topcutting into the face of the coal or both. Most of the coal mined is by undercutting alone, after which the machine is removed and a drilling machine is then brought to the face to drill shot holes, after which this machine isremoved and the coal is then blasted either by explosives or compressed gas in these shot holes to expand it and break it down. A loading machine is then brought to the face to load the coal on a conveyor or other means, from whence it is conveyed to the main entries of` the mine where it is transported by rail or belt to the surface. Present undercutting practice frequently creates steplike projections or offsets or loose and jagged conditions on both roof and floor which must be taken down, cleaned up and timbered.

Improvements in the art of deep mining coal have been confined principally to improved cutting bar machines, drilling machines, loading machines, bug-dusters and other supplementary equipment employed with4 such apparatus. However, the present practice and methods of deep mining follow the same cycle of undercutting, drilling blasting, loading and conveying which cycle has been practiced for centuries. Increased production in the past few years s due principally to the. improved ma-l chines for each individual phase of this coal mining cycle.

The shooting of coal by explosives or otherwise subjecting it to expansion or material vibration seriously damages the earths structure, which subsequently results in the production of falls that materially add to the hazard of deep mining. Blasting and vibrations incident tothe present mining cycle weaken the roof and ribs and create hazards to crews working in other sections of the mine.

Some machines are arranged to undercut a section. of coal and then break it down by vibratory picks. The cutting bar and the picks are presented alternately tothe coal face. This character of machine operates` in cycles with alternate periods of undercutting, then breaking down the coal. It is designed to operate on only a small portion of the face at a given time. The alternate presentation of the undercutter and the picks, together with the fact that it operates on only a partial section of the face, prevents this machine from functioning as a continuously progressing coal mining machine.

Continuons tunneling machines of the rotary cutting e type have been suggested in the art for tunneling in com.- bination with a conveyor. Such suggested machines were slow boring tools obviously intended to mille or grind through the earth and their cutters engage and bind on the perimetral surface of the tunnel. Although such machines were suggested they have never been practical. The foremost tunneling engineers still employ manually operated drills for tunneling.

The' art has also suggested the use ofv obviously impractical rotary machines for the mining of coalV which have rotary cutters provided with wedgesintended' to ICC break the coal but actually prevent the advancement of the cutters into the coal. Also the cutter supports bind against the'perimetral surface of the tunnel and thus they could not function as continuously progressing mining machines but represent mere ideas that do not have utility.

This invention overcomes the numerous difficulties inherent in the foregoing processes, and have provided method and apparatus for greatly increasing the production of a highly marketable coal economically and at a uniformly low cost, wherein the high percentage of fines and bug-dust have been eliminated.

The present invention contemplates apparatus for simultaneously cutting, preferably by chipping, removing and loading coal from the entire solid face in one single operation to accomplish what has heretofore required four steps in the mining cycle consisting of undercutting, drilling, shooting and loading. At the same time it eliminates the undesirable milling that produces bugdust andy fines and also the unsafe effects of shooting permitting the carrying out of simultaneous operations throughout the mine that are free from such hazards.

The cutting means, which per se constitutes an inventive feature, is provided with a plurality of cutters, preferably widely spaced radially, preferably progressively receding axially, and preferably connected by rearwardly spaced surfaces which may be sharpened, all mounted on a rotary head that cuts a series of annular concentric kerfs to free the coal from pressure and break it from the face and with the aid of scraping means continuously feed it to a conveyor. The use of such chipping cutters preents. the formation of fines or bug-dust in chipping the erfs.

The` cutting heads are preferably arranged in a plurality of banks with adjacent heads preferably in overlapping relation. Certain of said banks of cutting heads preferably lead others, advantageously in progressive sequence.A The opening cut by each head combines with openings cut by adjacent heads in thel same or different banks to form a single entry or opening.

Each of the outermost rotary cutting heads on the mining machines, which determine the size of theopening formed, is preferably dimensioned and mounted to cut clearance beyond the limits of the machine and to move toy a predetermined position out of contact with the perimetral surface of said opening.

The heads simultaneously sweep the freed coal laterally, preferably from the sides, in oppositevdirections, across the entire face to a conveyor which rapidly removes the coal. The sweeping action of the heads supplemented by blade scraping means removes all of the coal as the entry or room is driven, leaving a continuously smooth clean oor so that substantially no loose coal is lost or wasted and no manual cleanup is required'.

The apparatus herein taught represents a true continuous mining machine as it continuously cuts and removes the coal when forming its entries and rooms as the machine progresses through the coal. These improved mining conditions eliminate the inherent dangers of the f slow conventional' mining cycle methods wherein the interrupted steps in multiple operations accelerates oxidation and the resultant crumbling roof yet require the. repeated' return of men and machines to such areas for completing the mining cycle. In the apparatus as taught by this invention, coal is chipped from the solid very rapidly and the freshly cut roofs of the entries or rooms are driven forward at a speed hitherto unknown and are unaffected by oxidation and its resultant degradation, and no men need return or remain in a given area for any length of time as in the heretofore practiced mining cycle.

Other objects and advantages appear in the following description and claims.

The accompanying drawings show, for the purpose of exemplication but without limiting the invention or' claimsl thereto, certain practical embodiments of the invention wherein:

Figs. 1a and 1b together constitute a side elevation of the machine embodying the invention with portions omitted forsimpliiication;

Figs. 2a and 2b together `constitute a sectional View taken on the line 2-2 of Figs. 3a and 3b with portions omitted for simplification;

Figs. 3a and 3b together constitute a plan view of the structure shown in Figs. la and lb with portions omitted for simplification;

Fig. 4 is a front elevation of the machine;

Fig. 5 is a sectional view taken along the line 5-5 of Fig. 2a;

Fig. 6 is a sectional view taken along the line 6-6 of Fig. la;

Fig. 7 is a sectional view taken along the line 7--7 of Fig. la;

Fig. 8 is a plan view of the conveyor body;

Fig. 9 is a side elevation of a modified arrangement of the cutting heads;

Fig. 10 is a diagrammatic view of the machine having two sets of feed jacks in tandem; and

Fig. 1l is a diagrammatic view of the machine having two sets of feed jacks in parallel.

Referring to the drawings the coal mining machine consists of the hollow vehicle body 1 supported for movement by the independently controlled tracks 2 and 3 propelled by the driving sprockets 4 on each side of the front thereof and supported by the two sets of supports 5 and 6 having five bogie rollers each on each side thereof. The endless tracks are provided with grousers as shown in Fig. la. The upper flight of each track is supported by a pair of track support rollers 7 which are suitably journaled on the side of the vehicle body 1. The rear of the body 1 is supported by a pair of track idler wheels, such as illustrated at 8, one on each side of the body. The front driving sprockets 4 are secured to the outer ends of the axle 9, the intermediate portion of which is connected through a suitable differential 10 and transmission indicated at 11. Suitable conventional brake steering members are arranged when operated to lock the corresponding section of the axle 9 for the purpose of stopping one track while the other proceeds in order to turn the vehicle. p

The drive shaft 12 extends rearwardly from the transmission 11 and is mounted on the bearings 13 and 14. Intermediate the bearings 13 and 14 the drive shaft 12 is provided with a sprocket gear 15 and is driven by the driving chain 16 from the drive sprocket 17. The drive sprocket 17 is mounted on the end of the shaft 18 extending from the gear reducer 20. The inlet end of the gear reducer 20 is provided with the shaft 21 connected to the shaft 22 of the motor 23 by means of the coupling 24. The motor 23 is preferably a three-phase alternating current motor, the speed of which may be varied to control the speed of propulsion of the vehicle. However, the conventional transmission 11 is also provided with the gear shift lever 25 for the purpose of controlling the direction and speed of the vehicle. This transmission may be provided with four speeds forward and one speed reverse.

The propulsion motor 23 may be energized from the push button control 26 on a panel at the rear of the machine which functions to operate the line starter member 27. The trailing cable 28 is arranged to connect energy through the line starter 27 to the motor 23 and the cable extends rearwardly of the machine to any desired distance to a position where it is connected to the source of current for supplying electrical energy to the machine.

As shown in Figs. 1a and 3a two pairs of swiveled socket members 30 and 31 are secured to the upper and lower sides of the body 1 and are provided with arcuate sockets 32 arranged to receive the correspondingly shaped ends of the upper and lower parallel arms 34 and 35. The parallel arms 34 and 35 are also provided with aligned openings to receive the pivot pins 36 and 37, respectively, the center of which is common to the center of the arcuate bearing surfaces of the sockets 32. The parallel arms 34 and extend forwardly between the body 1 and their respective tracks to beyond the front end of thc machine and the forward ends of the lower arms 35 are integrally joined by the base plate 38. A knife digging blade is secured to the front edge of the plate 38 the assembly of which is referred to in the claims as the digging blade means. The cutting edge of the blade 40 is slightly higher than the outermost teeth of the lower cutter heads. The ends of the knife blade 40 flare outwardly and extend beyond the outermost portion of the tracks on either side of the machine. A pair of spaced box members 41 and 42 are secured at the outer side of the lower arms 35 and are formed integral with the outer ends of the base plate 38.

The box members 41 and -42 are each provided with aligned holes for receiving the pivot pins 43 and 44 arranged to extend through aligned holes in the box head plates 45 and 46. The box head plates are in turn secured to the lower end of the gear box or head 47 which extends substantially the full width of the machine. The rear side of the box is provided with two pairs of spaced lugs 48 and 49 each of which are provided with aligned holes to receive the pins 50 and 51 which pivotally support the front ends of the upper parallel arms 34. The eyes of the pistons 52 and 53 are also pivotally secured to the pins 50 and 51. These pistons operate in the hydraulic jack cylinders 54 and 55 respectively which are pivotally attached at their lower ends as shown at 56 and 57 to theirv respective bracket members 58 and 59 that are secured to the body 1 of the vehicle. These jacks are double acting and provide positive force for raising and lowering the scraping blade and the gear case or head pivotally attached thereto. These double acting jacks thus enable the digging means on the fore part of the machine to be adjusted relative to the body for the purpose of following the coal seam.

As shown in Figs. 4 and 5, the gear box 47 is fabricated from heavy steel plate and is provided with a scalloped bottom. The top of the box is provided with marginal flanges arranged to receive the lid 60 which is removable.

At uniformly spaced positions the front and rear plates of the gear box or head are provided with aligned bearings for receiving the upper and lower rows of forwardly projecting cutter head shafts S1 to Sio, inclusive, and the intermediate shafts M1 to M4, inclusive. The shaft Sz is arranged to receive power directly from the vehicle through the drive shaft 61, the universal joint 62 and the coupling 63.

As noted in Fig. 5, the shaft S2 is provided with a sprocket gear within the gear box which drives the shaft S1 through the chain 67. If the shafts S1 and S2 are arranged to drive the intermediate idler shafts M1 and M2 and the lower shafts S6 and lS7 through a train of gears as shown, the intermediate shaft Mz is also arranged to drive the shaft S3 by means of the chain 68. Thus, if the drive shaft 61 and the shaft S2 are rotated in a counterclockwise direction as viewed in Fig. 5 each of the shafts S1, S2, Ss and S7 will be likewise rotated in a counterclockwise direction, whereas the shaft S3 will be rotated in a'clockwise direction owing to the fact that its drive is received from the intermediate shaft M2.

Between the coupling 63 and the back of the gear box the shaft S2 is provided with a sprocket gear 64 arranged to drive the sprocket gear 65 on the shaft M3 by means of the roller chain 66. The idler shaft M3 rotates in a counter-clockwise direction. However, this shaft is likewise connected through gears to the shafts S4 and Ss and rotate these shafts in a clockwise direction. The intermediate shaft M3 is also arranged to rotate the shaft Sa by means of the chain 69 in a counter-clockwise direction. The shaft S4 is arranged to drive the shaft S5 in a clockwise direction through the chain 70 and the shaft S5, being connected by gears through the shaft M4, is arranged to drive the shaft S10 in a clockwise direction. By this arrangement of gear and chain drive both inside and outside of the gear box 47, five of the ten head shafts are operated in a counter-clockwise direction and the rest are operated in a clockwise direction.

While we have shown two horizontal tiers or banks of five drive shafts each, three or more of such tiers may be employed. By the same token either two or more than ve drive shafts may be employed in each tier.

The interior of the box is provided with the cross ribs 71, 72, 73, and 74, each of which is provided with suitable aligned openings or windows for receiving the upper and lower flights of the chains 67 to 70, inclusive. The lower ends of the brace ribs 71 to 74, inclusive, are also provided with windows to permit the inter-communication of oil within the gear box 47.

As shown in Fig. 2a, the upper shaft S5 does not extend as far beyond the end of the box 47 as does the complementary lower shaft S10 and the outer portion of each of these shafts is provided with the hexagonal surface indicated at 75 and 76 for the purpose of receiving the complementary hexagonal socket members 78 and 79 of the upper and lower cutter heads or digging members, arms, or breaker arms 80 and 81. The heads 80 on the arranged to cut counter-clockwise. and the. heads on shafts.v S3, S4. and S5: are duplicates with teeth arranged; to cut'.v

clockwise. Each head 80 is provided with a plate sec.- tion having three cusps 83., 83a. and 8312 which are pro.- vided with teeth but preferably have. socket members 85 for receiving. removable pairs of bits 86.. Each successive cusp. is positioned rearwardly and outwardly from the next preceding cusp and thus are. disposed alongza progressively receding angle. The centers of the socket members 75. are provided with central pilot post members 87' having a socket 8.8 for receiving unitary Y bits. 89.

The lower heads 81 on the shafts. Ss, S1 and Ss are duplicates. of one another with teeth arranged to cut counterclockwise and those on shafts S9. and S are duplicates with teeth arranged to cut clockwise. Each head 81 is likewise provided with the cusps. 90 and 91 on one side of the shafts, having. the sockets 85 for receiving the removable teeth or pairs of bits. 86. These heads are also provided with the pilot post members 87 having the sockets 88 for receiving the removable unitary Y drill head or bits 89. The heads 81 are. also provided with an opposed plate member 84 providing one cusp arranged to. support the. socket member 85 on which is mounted a pair of bits 86. The bits on the opposed plate members 84 are closer to the shaft than the bits on the cusps 91.

The upper and lower heads 80 and 81 are shown as having a central pilot head mounted on each shaft and at least two cusps which support teeth or pairs of cutting bits. The cusps are preferably offset at different positions relative to the axis of rotation of the cutter head for the purpose. of making their pair of bits, with the exception of the pilot bits, cut their own widely spaced annular kerfs in the face of the coal.

It should also be noted that each tooth or cutting bit 86 is disposed at an angle of between fteen and fty degrees, preferably approximately thirty degrees to the axis of rotation and that the projection of the longitudinal axis of each bit is disposed in the plane of, and along the chord of, its subtended arc of rotation, which plane is normal to the axis of rotation when viewed from they front of the cutting head.

The plates which form the heads 80 and 81 may be secured to the side of their respective socket members 78 and 79 as by welding, in which case the plates would be offset from the center of the axis of the sockets. The blades which form the heads 80 and 81 as defined in the claims as digging members or digging arms and are mounted eccentrically or non-concentrically on each shaft. Each of said digging means is mounted in anl off-center position on its shaft. All of the arm may extend outwardly from one side of the shaft as illustrated in the upper tier or a part of the digging member or arm may extend on opposite sides of the shaft as illustrated in the lower tier. However in each instance the arm is mounted in an off-center position relative to its own length. However, the cutting edges of the teeth or cutting bits 86, being disposed at an angle relative to the plates, all lie. in a plane passing through and extending longitudinally of the socket axis. When the heads are rotated and the vehicle is advanced, each pair of bits cut a helical kerf into the face of the coal. It is preferable to shape each bit so that they will cut a clearance for the shank of the bit. As the vehicle advances and the kerfs cut by the bits become correspondingly deeper, the coal intermediate adjacent bits, unless previously broken away, extends back toward the plate of the cutting head until it isv engaged onthe sides by the socket members 85 and the sharpened arcuate surfaces 92 between the cusps. The head is constructed so that the cutting bits from the pilot bit radially outwardly are disposed in successively receding positions in al plane axially of the socket. This arrangement of the cutting bits endows each head with a centering action tending to maintain the head in alignment with the axis of each shaft to eliminate lateral thrust. The'slow moving central bits which lead the faster moving outer bits and remove the central coal thereby enable the outer bits to function more efliciently in removing the balance of the coal. Much of the coal may be broken away ahead of the cutters due to its cleavage structure and friable nature.

lf the coal lying between the concentric kerfs is not fractured by reason of the normal vibration of the ma chine, the sockets 85 of the bits 86' will strike-it on the side of' the kerf andi wedge it laterally causing it to fracture and fall. The coal does not break away as a single piece vhutshatters in accordance: with its. cleavage.. structure and the action of thebrts may sometimesleave a circular protrusion. of coalwh'ich. will. be engaged. by. the sharpened. arcuate. surfaces 92 between the cusps. which chip. the coaland knoclcit out of; position- The lower shafts Ss to. Sie, inclusive, are arranged to protrude beyond the, upper row of shafts:- Si. to; S5, in clusive, so as to. provide clearance: or: arr undercutting' effect. which materially reduces the work of the upper row of cutting heads. To. permit maneuvering orwith drawal of the machine from; a singlezcut entry the cutting heads may be rotated to their positions. shownfin Fig 4 andthe gear box 47 raised by thejacks: 54 and 55. completely withdrawing the heads from the perimetral surface of the room. or entry cut.. The: same result may be obtained without manipulation of thejacks` byrotating the cutter headsv from: theirl positions.` shown in: Fig. 4 through a. small angle. sucient tu move the. outermost teeth of the lower: cutter heads: slightly above the; edge of the blade 40.

As shown in Figs'. 3a. and 6, thedrive. shaft 61'. passes through the opening 93 of the front of the vehicle, which opening is suitably shielded to prevent coal from entering the same. Thev shaft 95= has the'.v gear 98 connected thereto. intermediate of the bearings 96 and 97. This gear is arranged. to mesh. withthe. pinion. 99 on the intermediate drive shaft 100 carried.r bythe. bearings'101 and 102. The bearings 96 97,101?. and 102 arecarried. on the triangualr frame members 103, welded to the interior of the body 1 asshown in Fig; 7. The end of the intermediate shaft. 100. is: provided with thev coupling 104 which connects it to the output. shaft 105 of the conventional transmission 106A which may be controlledV by the gear shift lever. 107. The input shaft 108 of the transmission is' provided1 with. the coupling 109 for engagement with the: motor shaft 110 of the motor 111. The motor 111; is. likewise a preferably three-phasey alternating current. motorarranged to be energized from suitable. controls.. from. the same. source of power as that ofY the motor 23... The rnotor'111 is supplied with electrical energyy by" means: of the. cable 112. A push button 113l is. located'.l on the. rear push button panel for remotelyvv controllingv the energizationl of the motor 111 through a starting device adjacent the source of power not shown. The. propulsion motor 23.' and the rotary arm driving motor 1111together' with. the interconnected gearing. and transmission mechanism for supplying the energy from. these motorsk to the endless tracks and the rotary digging" arms; and the other mechanism mounted Within. the body ares enclosed and protected by the reinforced deck or: roof on: the body as. indicated in the drawing.

It will be noted that the cutting edge or blade 40 is located to the rear of the lower row of cutting heads and extends rearwardly to the point indicated at 114 in Figs. 2a and 4, which represents the. back edge of this blade lyingacross the front of the boxes 41 and 42. The opening between the boxes 41 and 42 on thel base plate 38 is arranged. to receivel the front end of the drag conveyor 115.

The conveyor 115- as shown in Figs. 2a, 2b, 7. and 8 comprises the spaced lower and. unner stationary troughs 116 and 1'17 respectively with the side walls 118 and 119. The conveyor 115 extends horizontally from the front to the back of thel vehicle and then slopes upwardly for the purpose of raisingthe coal. to a higher elevation to permit the insertion of a second conveyor 120 at the rear of the machine. At spacedv intervals the underside of the troughv is provided with the channeled cross braces 121. The forward end ofthe upper trough 117 of the conveyor is reinforced and is provided. with an inclined plate 123. A tube 124 is, secured to the' front edges of the trough 117 and. the plate 123 and is arranged to house. the shaft 125. The ends of the. shaft 125 are provided with the. sprockets 1'26 and 12.7 for receiving the conveyor roller chains 1'28 and 129 each consisting of a series of pairs of links. connected by crosspins on which. rollers 122 are mounted' for rotation. At spaced intervals the convevor chains 128 and 129 are connectedv by the crossbars130'which move therewith to drag the coal along the trough 11'7'. Suitable rails 131 and 132 are welded resnectivelyto. the upper surface of lower trough 116 to the underside ofthe brace members 121 to provide guidingI means. for` each ofthe. chains 128 and 129.. These rails liie'` between their' respective conveyor chain links and may be engagedby the rollers 122 as the chains pass between the upper and lower troughs 116 and 117 to hold the links of the chain.

out of engagement with the troughs. The clearance between the rails 131 and 132 is suicient to prevent the chain links and the crossbars 130 from striking the cross braces 121 but the space between the same is greater than the dimension of the roller of the chain to avoid simultaneous contact on the upper and lower surfaces of the rollers. A pair of chain rails 133 is also provided on the upper surface of the upper trough 117 to guide the conveyor chains along its rearward ight. Guide shoes 134, Fig. 2a, are secured to the inner surfaces of the front end of the sides 118v and 119 to hold the conveyor chains with proper clearance as they pass under the gear box 47. The opening between the scraper blade assembly and the lower side of the gear box is referred to in the claims as an aperture. If the coal .that is dug by the rotary digging arms is too large to pass through this aperture the arms break up the coal by sweeping it towards each other and jamming it between themselves and between any part of the machine such as the gear b ox or the blade assembly or the oppositely rotating arms. When the coal is of sufcient size to pass through the aperture a conveyor will move it to the rear of the machine. A similar shoe 135, Fig. 2b, is placed on both sides at the bend of the conveyor for the purpose of preventing the chains and the crossbars from lifting from the tray of the conveyor as it passes rearwardly on its upward flight.

At the rear end of the conveyor the sides are provided with the crosshead guides 136 having aligned slots 137 through which passes the shaft 138. Sprockets 144 and 145, secured to the shaft, are employed to drive the respective chains 128 and 129. A pair of bearing blocks 140 are grooved on their upper and lower edges to t and slide along the crosshead track rails 141. An adjusting screw 142 is threadably engaged in each of the lugs 143 secured to the plates 136 for the purpose of adjusting the shaft 138. to provide a takeup for the conveyor chains. .These adjusting screws may also be employed for properly aligning each end of the shaft 138. The intermediate portion of the shaft extends through the tubular casing 139 which is welded to the adjustable plate 117 that slides under the upper trough 117 of the conveyor and is guided in spaced relation above the return ight of the conveyor bars.

The shaft 138` extends beyond one side of the conveyor and is provided with a shaft supported speed reducer 146, the housing of which is held from rotation by the rod 146 attached to the side of the conveyor. The other side of the speed reducer is provided with a pulley 147 having a plurality of grooves for receiving the V-belts 148 which encircle the drive pulley 149, operated by the motor 150 supported on the frame 151 secured to the top of the conveyor. The conveyor motor is preferably a three-phase motor of the'same voltage as the motors 23 and 111 so that it may be operated from the same source of power but with separate controls as it may be desirable to run the conveyor when the propulsion motor 23 and the cutter motor 111 are not being operated.

The conveyor 115, with its enclosed return ight and exposed load conveying ight, is arranged to operate at a speed to remove all the coal from the vicinity of the cutting heads at a rate faster than the cutting machine is capable of digging the coal. The front end of the conveyor rests on the base plate 38 between the boxes 41 and 42 and the rear end of the conveyor is supported by the links 152 depending from and secured to the rear of the vehicle. The under tray 116 of the conveyor is supported above the surface of the ground.

Referring again to Fig. 4, it will be noted that the four cutter heads on the shafts S1, S2, Ss and S1 rotate in a counter-clockwise direction for the purpose of conveying or sweeping the coal from one side of the machine to the conveyor 115 at the center, whereas the cutter heads on the shafts S4, S5, S9 and S10 are rotated in a clockwise direction for the purpose of conveying or sweeping the coal in the opposite direction to the conveyor 115 at the center of the machine. Thus, the extreme outer cutting heads of the upper and lower rows not only cut the coal but also act as a conveyor for moving the coal to the center of the machine where it is picked up by the chain conveyor 115. The heads thus prevent the coal from falling along the side of the machine.

It should also be noted that the cutter heads of the their overlap, as shown in Fig. 4. This may be illustrated by the fact that the cutting circle of an intermediate -bit of the cutter head on the shaft S1 cuts from point A to point B which cutting circle may be substantially in the same vertical plane as the cutting circle of the outer bit of the cutter head on shaft Ss which cuts from point B to point C, as shown in Fig. 9. The outermost bit of the cutter head on the shaft S1 cuts from the point D to point E. The intermediate cutter heads on the lower shaft S7 will cut between the points C and F, whereas the outermost part of the cutter head on the shaft S2 will cut from points G to D. The other intermediate cutting heads will likewise perform a similar cutting action.

As the vehicle is propelled forwardly the upper and lower rows of rotary cutter heads cut a series of corre sponding circular openings or kerfs in the coal leaving a series of cusps on the roof, walls and oor of the mine. The cusps formed betwen the lower cutting heads are removed by the cutting blade 40. The cusps formed between the upper cutting heads may be removed from the roof by the cutting blade 153 which is adjustably positioned on the gear box 47 by means of the hydraulically controlled jacks 154. However, portions of the cusps of coal formed by the upper cutting heads frequently fall to the conveyor owing to the fact that the vibration fractures the same as the machine proceeds through thc coal.

Adjustable cutting blades 155 and 156 may also be ernployed on the sides of the gear box 47, as shown in Figs. 3a and 4, for cutting the kerfs between the upper and lower cutting heads on shafts S1, Se, S5 and S10, respectively. Thus, by the use of the four knife blades a single tunnel with uniform ceiling, oor and walls may be mined. The cutting knife blades 155 and 156 may be supplemented by the side aps or shields 157 and 158 for preventing any coal from working beyond the sides of the gear box. These shields guide the coal down toward the mouth of the conveyor and are arranged so that they will extend outwardly to substantially tit the extreme cutting kerfs of the upper and lower cutting heads with a slight clearance but if the machine is retracted or reversed these shields are arranged to fold inwardly toward the gear box to enable maneuvering of the machine.

Each of the shafts S1 to S10, inclusive, are maintained in timed relation and are preferably provided with, say, hexagonal ends to permit the proper positioning of the cutting heads thereon so that as they rotate they will not interfere with one another because of the overlapping arrangement of the cutting heads as previously disclosed. In order to maneuver the machine when it is not cutting it is preferable to rotate the heads to position them downwardly as indicated in Figs. la, 2a and 4 and energize the jacks 54 and 55 to raise the whole of the front assembly which is guided by the two sets of parallel arms 34 and 35. Thus, by raising the whole of the front assembly the machine may be maneuvered within the passage that has been cut with suicient clearance to guide or retrack the machine or to redirect the tunnel at an angular position, horizontally from the previous cut.

The jacks 54 and 55 may also be regulated to raise or lower the front assembly and thereby enable the operator to follow the vein of coal as it changes in elevation.

The term chipping is employed herein to designate the action of a tool point in picking, cracking or breaking off as well as cutting its way through virgin coal.

The action of the tool point or bit on the overlapped cutting heads in conjunction with the cleavage planes in the coal cause large chunks of coal to be dislodged from the solid ahead of the bits and conveyed from the machine, particularly when the bits of a cutting head approach the clearance formed by the bits of an adjacent cutting head or enter the coal from the clearance formed by an adjacent cutting head. In fact large chunks of coal are found with half of the bore formed by the pilot bits of the upper cutting heads with virgin coal in front of the end of the bore, which chunks are evidently dislodged when the coal breaks loose due to the advanced position of the lower cutting heads. The majority of large chunks of coal are dislodged by bits other than the pilot bits as they show a single bit mark with no other marks on the lump of coal. The coal removed by this machine has a very low percentage of fines but practically no bug-dust. The large lumps produced by the bits shown are approximately from six to eight yinch cubes. he heads function to crush the very large lumps between themselves and between the heads and the gear box or the blade but the actual size of the coal removed can be predetermined to a fair degree of accuracy by regulating the factors which are responsible for the removal of thc coal, such as the angular position and the spacing of the bits on each head, the overlap of adjacent heads, the lead of one tier of heads relative to the others, the speed of rotation of the heads, and the speed of advance or feed of the machine into the virgin coal. The chipping helix due to the speed of the heads Vand the advancing feed may be read by the scoring of the bits onthe sides of the entry as well as on some of the chunks of coal removed by the machine. It is apparent that when the rotating heads .are advanced into the virgin coal each bit cuts along a predetermined helix and the pitch of the helix varies with the speed of advancement into the virgin coal. It is also evident that the cleavage planes of the coal aid in the removal of the coal as the rotary bits are continually crossing these planes as they advance into the coal.

The feed or advance of the machine may be obtained by one or more modes such as the independently controllable endless tracks 2 and 3 or by a positive feed means such as the double acting jacks :160 and 161, Figs. 1b, 2b and 3b, which are pivotally secured to the respective saddle members 162 and 163 that bridge the tracks 2 and 3 and are secured to their framework and to the body of the tank. Under some conditions the endless tracks 2 and 3 are capable of providing the necessary feed of the machine into the coal but when the weight of the machineis insuflicient the rubber tired roof wheels 164, .rotatably mounted on the eleva-tor 165 operated by the hydraulic jacks 166, are raised to exert pressure on the roof for the purpose of increasing the traction load on the endless tracks which may be provided with additional spaced cleats, to increase the tractive effort. The connecting section of the elevator 165 that lies across the machine is hinged adjacent the opposite pairs of wheels 164 to permit one pair of roof Wheels to be higher than the other to allow for unevenness in the roof structure. The wheels 164 are set to ride in the channels formed by the heads on the shafts S2 and S4.

4When the supplementary load to increase tractive effort by the heavy hydraulic elevator jacks 166 is not feasible or sufficient, lthe positive hydraulic feed produced by `the feed jacks 160 and 161 may be used alone or in vconjunction with the endless tracks 2 and 3 and the elevator 165. The feed jacks 160 and 161 are arranged to expand against the roof jacks 167 and 168 each of which consists of a lower bell crank leg member 170 having an artillary spade 171 and ground pad 172 on one arm and the skid 173 on the other arm. The upper leg member 174 is the longer and is provided at its end with a hinged roof pad, or shoe, 175. The upper and lower sets of 'roof jack legs 174 and 170 are pivotally connected to eachother and to the outer end of their respective doubleacting feed jacks 160 and 161 by means of the toggle pivot pins 176 and are expanded or contracted against the roof and oor by the double-acting hydraulic jacks 177 and 178.

The two roof jacks 167 and 168 are tied together vby the upper and lower cross members 180 and 181 which are pivotally secured to each roof jack member so as to allow relative movement to each other. When the expansion jacks 177 and 178 are extended to push the roof pad 175 against the roof and the artillary spades 171 into the ground to set the roof jacks, the hydraulic pusher feed jacks 160 and 161 may be expanded to push against the 'toggle pivots of the roof jacks and move the machine forward. The rate of feed forward may be regulated by the manual control valve at the operators station. The .starter push button 182 functions to energize the motor 183 that operates the hydraulic pump 184 for supplying vhydraulic pressure for each of the jacks on the machine. It is preferable to slowly move the machine with the heads rotating into engagement with the face of the coal and when the bits start to cut into the coal the feed pressure is increased gradually until both roof jacks are firmly set and the feed jacks are equally expanded to move the machine into the coal. The hydraulic pressure on the feed jacks is then increased until the machine advances a predetermined number of feet per minute into the virgin coal. By controlling the supply of fluid to only oneh feed jack the machine may be directed in an arcuate pa By `using only one set of roof and feed vjacks the movement of the machine is of course intermittent requiring the roof jacks 167, 168 and the feed jacks 160, 161 to be retracted at the end of each feed stroke but continuous positive feed may be obtained by duplicating the sets of roof and feed jacks so that the first set may be function-- ing to feed the machine while the second set is being retracted and positioned to enable it to take on the feed before the first pair are fully expanded. With this arrangement one set may be disposed in tandem with the other set as shown diagrammatically in Fig. l0 wherein the rear set of roof jacks 184, and the rear set of feed jacks 136, 187 have been added and the latter being constructed to expand at a faster rate to collapse the first set of feed jacks 160, 161 while continuing to move the machine forward at the same rate of speed imparted to it by said first set of jacks. The alternative is to place the two sets of jacks in parallel as shown in Fig. ll wherein the set of feed jacks 160, 161 and their roof jacks 167, 168 are placed in parallel with the duplicate set of feed jacks 18S, 189 and their roof jacks 190, 191. These sets are positioned side-by-side but are separately controlled to automatically provide a positive continuous feed motion to the machine. The valves controlling the hydraulic operation of these double-acting jacks are arranged to expand one set of feed jacks and before they reach their ultimate expanded position the other set is placed and the feed jacks expanded so as to operate with the first set during the load transfer. When the load is 'transferred to the newly added jacks the other set is quickly retracted to be in readiness to again take over the feed load and thus maintain continuous movement of mining machine into the coal.

While, for clarity of explanation, we have shown and described certain preferred embodiments of our invention, it is to be understood that it is vcapable of many modifications, that changes in construction and arrangement may be made therein and that certain parts may be employed without conjoint use of other parts without departing from the spirit and scope of our invention.

We claim:

l. ln a mining machine, the combination of a mobile body, means to propel said body, a plurality of forwardly projecting rotary shafts having digging arms provided with cutter means ycarried on the forward end of said body for driving attunnel, each digging arm and its cutter means adjacent the perimeter of said body being eccentrically mounted on its rotary shaft and extending beyond the perimeter of said body to cut the crosssectional dimension of the tunnel, all of said cutter means being materially and .simultaneously out of conr tact with the floor, ceiling and walls of the tunnel at predetermined positions of rotation of said digging arms.

2. In a mining machine, the combination of a body mounted upon differentially controlled endless propulsion tracks, an upper and a lower pair of parallel arms pivotally mounted on the sides of said body and extending forwardly, a horizontal scraping blade secured to the forward ends of the lower arms with its ends extending beyond the endless tracks, hollow supports secured in spaced relation to the rear side of the scraper blade to form a socket intermediate the ends -of the blade, a gear box pivotally .supported on the hollow supports and pivotally attached to the forward ends of the upper pair of parallel arms, an upper and lower series of shafts extending from and rotatably mounted to operate in timed relation to the gear box, a motor with reduction for driving said shafts, a conveyor having its forward end stepped in and carried by said socket and extending rearwardly of the body, a motor carried by the body for driving the conveyor, a chipping head on each shaft, the shafts of the outermost chipping heads rotating outwardly and downwardly to sweep the material to the conveyor, and means for raising and lowering the gear box and blade relative to the body.

3. In a mining apparatus, the combination of a mobile machine having two rows of forwardly extending rotary shafts, digging arms having removable bits mounted on said shafts each of said digging arms lying wholly on one side of the shaft on which it is mounted to extend the path of the outer bits beyond the perimeter of the machine, the digging arms in each row 'having overlapping paths in the same plane and the digging arms of the upper row partially overlapping the paths of the digyging arms of the lower row, means to propel said machine into a coal seam and permit the rotary digging arms to cut a tunnel therein, and a conveyor for removing the coal freed by the rotary digging arms.

4. A continuous coal mining machine comprising a mobile body, means to propel said body, a head mounted on the forward part of said body, a series of spaced forwardly projecting rotary shafts carried on the front of said head, power means for driving said shafts, a digging member eccentrically mounted on each shaft, cutting bits mounted on each digging member, the cutting bits on each digging member travelling in paths concentric to the axis of rotation of the shaft on which said member is mounted, the paths of the outer bits extending beyond the perimeter of said mobile body and said head, said digging members cooperating to mine the whole of the area of the face to cut a tunnel.

5. The structure of claim 4 characterized in that said head is of greater lateral dimension than the body.

6. The structure of claim 4 characterized in that the eccentrically mounted digging members are positioned adjacent to the perimeter of said head.

7. The structure of claim 4 which also includes conveying means carried by the machine, said eccentric arms cooperating to move the coal to the conveyor.

8. The structure of claim 7 which also includes means defining an aperture in the lower portion of said head through which the coal is carried by said conveying means 9. The structure of claim 4 characterized in that said shafts are so spaced that the paths of the adjacent eccentrically mounted rotary digging members overlap one another in their rotation.

10. The structure of claim 4 characterized in that said shafts with their eccentrically mounted rotary digging members are disposed in upper and lower tiers, the rotary paths of the eccentrically mounted rotary digging members in either tier overlapping the rotary paths of the adjacent rotary digging member of the other tier.

11. The structure of claim 10 characterized in that said lower tier of shafts with their eccentrically mounted digging members are positioned in advance of the upper tier.

12. The structure of claim '4 which also includes adjustable means for moving said head relative to the body.

13. The structure of claim 4 which also includes a oor scraping and digging blade supported on the body and having a cutting edge extending continuously across the front thereof.

14. The structure of claim 13 characterized in that said blade is pivotally attached to be adjustable relative to said body.

15. The structure of claim 4 characterized in that the said power means for driving said shafts is mounted in said mobile body, and a reinforcing deck enclosing the top of said body to protect said power means and other mechanism therein.

16. A continuous mining machine comprising a mobile body, a series of spaced forwardly projecting shafts carried by said body, power means for driving said shafts, an outwardly projecting digging arm mounted non-concentrically on each shaft and provided with spaced bits, the paths of the outer bits extending beyond the perimeter of said mobile body, said arms cooperating to simultaneously mine the whole of the area of the coal face to form a tunnel, said arms so positioned non-concentrically on their respective shafts that they are rotatable to positions where the machine and arms and bits are a substantial distance from the perimeter of said tunnel to permit the machine to move freely therein, and independently driven endless tracks supporting said body and forming a part thereof and providing the means for feeding and guiding the rotary digging arms into the coal seam.

17. The structure of claim 16 characterized in that said endless tracks are constructed to provide extended bearing surface fore and aft of the center of gravity of the machine.

18. The structure of claim 16 which also includes grousers on said endless tracks to provide positive tractive effort in feeding the rotary digging arms.

19. A continuous coal mining machine comprising a main mobile body, means to propel said main body, a gear box having a front face with an opening in the lower portion thereof, pivot means carried by and positioned forwardly of said main body to support salidtV gear box. a plurality of spaced forwardly projecting rotary shafts extending out of the front face of said gear box, power means for driving said shafts, an outwardly projecting digging arm mounted on each shaft, cutting bits mounted on each digging arm to cut a tunnel, a conveyor carried by said body and having its forward end supported by said gear box opening and movable with the gear box for conveying coal rearwardly from said gear box and means to pivotally move said box and digging arms relative to the body.

20. The structure of claim 19 characterized in that said means to adjust said gear box is a double acting power means to apply positive pressure in adjusting the position of said digging arms relative to said body.

21. The structure of claim 19 characterized in that said power means for driving said shafts on said gearbox is mounted in said main body and includes universal joint means connecting said power means and said shafts on said gearbox.

22. The structure of claim 19 characterized in that said means attaching the said gearbox on the front of said main body comprises arms pivotally attached to both said main body and to said gearbox.

23. A continuous coal mining machine comprising a mobile body, means to propel said body, a head mounted on the front of said body and pivoted to said body, a plurality of spaced forwardly projecting rotary shafts carried on the front of said head, power means for driving said shafts, an outwardly projecting digging arm mounted on each shaft, a oor digging and scraping blade means extending across the front of said body and pivotally supported on the bottom of said said head and on on said body and projecting forwardly thereof and sufficiently wide to the cut the oor cusps formed between adjacent digging arms, said digging arms cooperating with said digging blade means to dig and feed the coal to a common point, and means to adjust said blade means and head on their pivotal supports to move them relative to said body to tilt said head and blade means while digging a tunnel to facilitate changing the vertical direction of digging.

24. The structure of claim 23 characterized in that said means to adjust the blade means is a double acting power means to apply positive pressure in raising and lowering said head and blade means.

25. A continuous mining machine comprising a mobile body, means to propel said body, a head, pivot means supporting said head at the front of said body, a plurality of spaced forwardly projecting rotary shafts carried on the front of said head, power means for driving said shafts, an outwardly projecting digging arm mounted on each shaft, a oor digging and scraping blade means attached to the bottom of said head and sufficiently wide to cut the oor cusps formed between adjacent digging arms and positioned below the forwardly projecting shafts, said digging arms cooperating with said digging blade means to dig and feed coal to a common point, and means to adjust said head and blade means on said pivot means relative to said body, an aperture between said head and said blade means, conveying means carried by the body and having its forward end supported on said blade means in said aperture, said blade means sloping upwardly toward said conveying means, said blade means and said digging arms cooperating to move material to the conveying means.

26. A mining machine comprising a body, a gear case means pivotally secured to the front thereof, a blade means pivotally secured to the forward end of said body, means to pivotally secure the gear case means to said blade means, an aperture between said gear case means and said blade means, a series of spaced forwardly propecting shafts on the front of the gear case means, means to drive said shafts, an arm mounted on each shaft, a conveying means having its forward end supported by said blade means and positioned to convey coal through said aperture, means to propel the machine forward with the arms rotatably engaging and sweeping the material laterally toward the conveying means, the cooperative action of said rotating arms, blade means, gear case means and conveyor crushing any material to a size limited by said aperture.

27. The structure of claim 26 characterized in that the outer of said arms sweep in opposite directions to- Ward th@ conveying means.

28. The structure of :claim 26 characterized `in that said gear case means and blade .means are adjustable relative to said body.

29. A rotary coal digging head comprising a .hub having a bore for mounting on a rotary shaft, an outwardly extending breaker arm lcccentrica'lly mounted on said hub, widely spaced cusps on the .front edge of said breaker arm, each successive cusp positioned outwardly from the next preceding cusp, bit means mounted on each cusp and cooperating with said breaker arm whenm operation to break .coal out .toward the cavity formed by each preceding bit means, said `arm simultaneously sweeping the loose coal.

30. The structure of .claim 29 characterized in .that the cutting edges of said bits lie in a receding line .to a plane normal to the axis of rotation.

3l. The structure of .claim 29 which also includes a second and shorter breaker arm 'extending from said hub and having a cusp with bit means.

32. The structure of claim 29 characterized in vthat said bits are mounted on each cusp at an angle relative to said arm.

33. The structure of .claim 29 .characterized in .that the longitudinal axis .of said bits are disposed at an angle to the axis of rotation of said shaft.

34. The structure of claim 33 characterized in that said rangle is from sixty to ninety degrees. i

35. A continuous mining machine comprising a .mobile body, means to propel said body, a head mounted on the front of said body, a series of forwardly projecting rotary shafts in each of a pluralityof tiers mounted on said head, interconnecting drive Ameans in said head for rotating said shafts in timed relation to each other, power means for' rotating said interconnecting drive means, a digging member mounted on each of said shafts, spaced bits mounted on said digging members which cooperate to mine the whole of the area of the face to cut a tunnel, the combined length from the shaft center of one end of each digging member and its outermost bit being longer than the other end of said digging member and its outermost bit, said shafts being spaced laterally so that the path of the outer bit on each digging member extends beyond the perimeter of said body and overlaps the paths of the outer bits of each laterally adjacent digging member, the intersecting segments of the paths of said outer bits defining the perimeter of the tunnel.

36. The structure of claim 35 characterized in that said tiers are spaced vertically so that the path of the outer bit on each digging member overlaps the paths of the outer bits of the laterally and vertically adjacent digging members.

37. The structure of claim 35 characterized in that the path of the outer bit on each digging member overlaps the paths of the outer bits of the laterally and vertically and diagonally adjacent digging members.

38. The structure of claim 35 characterized in that the path of the outer bit on each corner digging member overlaps the paths of the outer bits of at least three of the adjacent digging members.

39. The structure of claim 35 characterized in that the path of the outer bit on each intermediate digging member overlaps the paths of the outer bits of at least five adjacent digging members.

40. A continuous mining machine comprising a mobile body, means to propel said body, a head mounted on the front of said body, a series of forwardly projecting shafts in each of a plurality of tiers mounted on said head, an eccentric digging member mounted on each of said shafts, spaced bits mounted on said digging members each cooperating to mine the whole of the area of the face to cut a tunnel, the paths of the outer bits extending beyond the perimeter of said mobile body, central passage means in said head to receive material for conveying it rearwardly of the machine, drive means within said head to rotate said shafts and their digging members in groups of a plurality in each tier in opposite directions, the digging members of the upper tier moving the material toward the digging members of the lower tier which in turn sweep the material to said central passage means, and power means for operating said drive means.

4l. A continuous mining machine comprising a mobile body, means to propel said body, a head mounted on the front of said body, a series of five forwardly projecting shafts in each of two tiers mounted on said head,

.an eccentric digging member mounted on .each of said shafts, spaced bits mounted on. said digging .members which cooperate to `mine the wlhole of the area '.of the face to cut a tunnel, the paths .of the outer bitsextending beyond the perimeter of said mobile body, central passage means in said head to receive material for conveying it rearwardly of the machine, drive means within said head to rotate the shafts of three digging members in one direction and two digging members in the opposite direction in each of said 'two tiers, the digging members of the upper tier moving the material toward the digging members of the lower tier which in turn sweep the material .to said central passage means, and power means to operate said 'drive means.

42. A continuous coal mining lmachine comprising a mobile body, means to propel .said body, a head mounted on the front of said body, .a plurality of spaced for wardly projecting rotary shafts carried on the front of said head, power ymeans for driving said shafts, an outwardly projecting digging arm `mounted on each shaft, scraping blade means pivotally v.supported about a horizontal axis on the top `ofsaid head and suiciently wide to extend the width of the body to cut the roof Acusps formed between 4adjacent digging arms and means to raise and lower said blade about its pivotal support.

43. A continuous `coal mining machine comprising a mobile body, means to lpropel said body, a head mounted on the front of said body, .a plurality of spaced forwardly projecting rotary shafts carried on the front of said head, power means .for driving said shafts, an outwardly projecting digging arm mounted on each shaft, a floor ydigging and scraping blade means pivotally supported about a horizontal axis on the bottom of lsaid head and sufficiently wide to extend the lwidth of the body to cut the floor cusps formed between .adjacent digging arms and positioned below the forwardly projecting shafts, a scraping blade means pivotally supported about a vertical axis on each -side 'of said head, and independent means .to adjust each yof said blade means about their pivotal supports relative to said head as the machine continues to cut a tunnel through the coal.

44. A continuous coal mining machine comprising a mobile body, .means to .propel said'body, ahead mounted on the front of said body, a plurality of spaced forwardly projecting rotary shafts carried on the front of said head, power means for driving said shafts, an outwardly projecting digging arm mounted on each shaft, a door digging and scraping blade means pivotally supported about a horizontal axis on the bottom of said head and suiciently wide to extend the width of the body to cut the floor cusps formed between adjacent digging arms and positioned below the forwardly projecting shafts, a scraping blade means pivotally supported about a vertical axis oi each side and the top of said head, said digging arms cooperating with said blade means to dig and feed coal to a common point, and independent means to adjust each of said blade means about their pivotal supports relative to said head as the machine continues to cut a tunnel through the coal.

45. A continuous coal mining machine comprising a mobile body, means to propel said body, a plurality of spaced forwardly projecting rotary shafts carried on the front of said body, power means for driving said shafts, an outwardly projecting digging arm mounted on each shaft and having bits to cut a tunnel, means on the side digging arms for mounting them in an offcenter position on their respective shafts but permitting them to travel in concentric paths to their shafts, the paths of the outer bits extending beyond the perimeter of said mobile body, said side digging arms being out of contact with the sides of the tunnel at predetermined rotary positions to permit the machine to maneuver laterally in the tunnel.

46. A coal mining machine comprising a body, a substantially vertically disposed dust confining shield protecting substantially the whole of the forward end of said body, a plurality of powered rotary shafts extending out of and projecting forwardly from said shield, digging arms on said shafts, a rigid blade having a continuous cutting edge mounted on the bottom of said shield and sloping downwardly and forwardly to a point lower than the bottom of said shield and effectively extending the same, a throat in the lower portion of said shield to receive and convey coal rearwardly of said body, and powered endless track on each side of said the coal face to free the coal and advance the face and Y simultaneously scrape the cutting edge of said blade along the floor to prepare the oor for said endless tracks and to co-operate with said shield to crowd the loose coal into said throat. I,

47. The structure of claim 46 which also includes a second rigid blade having a continuous cutting edge and projecting upwardly to a point higher than the top of said shield and for the width thereof to scrape the cusps on the ceiling as the endless tracks feed the body forward and to extend the upper portion of said shield.

48. The structure of claim 46 characterized in that said digging arms are rotated in a selected direction and cooperate with said shield and said blade to move the loose coal toward said throat.

49. The structure of claim 46 characterized in that said endless tracks are operable independently of each other with adjustable speed for mining at an angle to the single hole made by one pass of the machine.

50. The structure of clairn 46 characterized in that said endless tracks are provided with grousers which mesh with the mine floor to provide a gear-like traction to feed the mining machine into the coal face.

5l. The structure of claim 46 characterized in that the back of said digging arms are shaped to extend in close proximity to the sloping top surface of the blade to cooperate therewith in sweeping the loose coal laterally.

52. A continuous coal mining machine comprising a body, a plurality of forwardly projecting power driven rotary shafts on the forward end of said body, digging arms mounted on said shafts and having cutters for continuously mining the entire face of a tunnel through which the machine can travel, the combined length from the shaft center of one end of each digging arm adjacent the perimeter of said body and its outermost cutter extending beyond the perimeter of said body and being longer than any other part of said digging arm and its outermost cutter, a throat in the forward end of said body for receiving and conveying coal rearwardly of said body, endless track means on each side of said body, means for controlling the speed and direction of said endless track means to control the pressure and direction of said digging arms into the coal face, and means to control each of said track means independent of the other to change the direction of the tunnel while the machine is advancing the coal face.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,148,973 Kuhn et al. Aug. 3, 1915 1,148,974 Kuhn et al. Aug. 3, 1915 1,353,142 Bohen Sept. 2l, 1920 1,361,734 Katulka Dec. 7, 1920 1,532,243 Hebsacker Apr. 7, 1925 1,603,621 McKinlay Oct. 19, 1926 1,639,215 De Grassi Aug. 16, 1927 1,645,007 Johansen Oct. 11, 1927 1,674,870 Morgan June 26, 1928 1,726,963 McKinlay Sept. 3, 1929 1,809,351v Oliver June 9, 1931 1,862,230 McDermott June 7, 1932 1,873,240 Wright Aug. 23, 1932 1,888,085 Humbel Nov. 15, 1932 1,915,001 McKinnon June 20, 1933 2,030,063 Halleck Feb. 11, 1936 2,083,834 Galuppo et al. June 15, 1937 2,287,230 Cartlidge June 25, 1942 2,415,217 Osgood Feb. 4, 1947 2,420,755 Mavor May 20, 1947 2,599,042 Bannister June 3, 1952 2,606,010 Howard Aug. 5, 1952 FOREIGN PATENTS Number Country Date 17,786 Great Britain July 27, 1914 26,289 France June 12, 1923 65,280 Germany Nov. 7, 1892 OTHER REFERENCES Coal Age, May 13, 1926 (pp. 668-670). Coal Age, April 1933, pp. 111, 112 and 127, and May 13, 1926, pp. 667-670. 

